A column of Russian tanks and armoured vehicles left the Georgian city of Gori on Tuesday in what Russian officials said was the start of the pull-back demanded by the West.
A Reuters reporter saw four armoured personnel carriers and up to three tanks start up their engines and move out of Gori, which Russian forces had occupied this month in a conflict over Georgia's breakaway South Ossetia region.
The move followed a NATO call for Russia to respect a peace deal with Georgia and pull out its troops, although alliance members were cool on a U.S. demand that NATO consider scaling back ties with Moscow.
"This is one of the first units to be pulled out," said an official from Russia's foreign ministry, which arranged for reporters to watch the column leave. The unit's commander said they were heading for the Russian city of Vladikavkaz.
It was not immediately clear if other Russian units were also pulling out of their positions inside Georgia.
Russia agreed to pull its forces back under a ceasefire deal brokered last week by French President Nicolas Sarkozy. Russian troops went in after crushing a Georgian attack on Moscow-backed South Ossetia.
Until Tuesday there had been no evidence of the ground that Russian forces were on the move, and Western pressure to observe the ceasefire had been mounting.
"What is at issue today is making a lasting ceasefire out of the still very fragile situation, the very delicate situation in Georgia," German Foreign Minister Frank-Walter Steinmeier said as he arrived in Brussels for a NATO ministers' emergency meeting. "We therefore urge Russia to pull out of core Georgia."
The NATO meeting was to discuss a U.S. suggestion to punish Russia by suspending alliance ministerial meetings with Moscow. It was also expected to restate a commitment to eventual NATO membership for Georgia, angering Moscow but pleasing Tbilisi.
TENSIONS
Stepping up pressure on Tbilisi, Moscow closed its land border with Georgia and neighbouring Azerbaijan to citizens who are not from the CIS, a grouping of former Soviet states. Georgia last week said it was pulling out from the CIS.
A decree signed by Prime Minister Vladimir Putin said the move was needed to "prevent weapons smuggling and members of foreign terrorist organisations from entering Russia".
The head of Russia's main domestic spy service, the FSB, Alexander Bortnikov ordered extra security to foil what he said was a plan by Georgian security to carry out "terrorist acts" inside Russia.
Georgia dismissed the accusation as "complete nonsense".
Air, rail and sea links between Russia and its former Soviet vassal Georgia have already been cut. The virtual blockade has hurt Georgia's economy, which depends heavily on Russia.
Conflict erupted over South Ossetia when Georgia sent in troops and tanks to try to take back the province on August 7-8, provoking a huge counter-attack from Russia.
Western powers have condemned Russia's response as disproportionate while Moscow says it was necessary in order to protect Russian citizens and Russian peacekeepers in South Ossetia and prevent Georgia carrying out a "genocide".
The Russian military campaign has been popular at home. A poll published on Monday found that 37 percent of respondents agreed with President Dmitry Medvedev's actions, while a quarter felt he should have been tougher still with Georgia.
In Moscow, deputy chief of the military's general staff Anatoly Nogovitsyn said Russia was pulling back its forces to South Ossetia.
But he said the process would be a gradual one because Moscow wanted to make sure the security situation in the areas of Georgia it was vacating was stable.
Earlier, the commander of Russian forces in the central Gori region, Major-General Vyacheslav Borisov, said he was still waiting for the order to withdraw from Georgia proper.
"I haven't received any order informing me about that," he told reporters.
In a rare sign of cooperation on the ground, Russia and Georgia did conduct an exchange of prisoners on Tuesday on the main road in the village of Igoeti in central Georgia, about 45 km (28 miles) from the capital Tbilisi.
PRESSURE ON SAAKASHVILI
Some analysts think Russia may drag its feet in pulling out its troops to keep economic and social pressure on Georgian President Mikheil Saakashvili and on his pro-U.S. government, which Moscow strongly dislikes.
Others believe Moscow may not intend to leave and is more likely to advance its forces on the Georgian capital, something Russian commanders have always said they do not plan.
"You have to ask yourself why they are here still," Tornike Sharashenidze, a professor at the Georgian Institute for Public Affairs, told Reuters.
"They are expecting a provocation or they will mount one themselves. Who knows? it only needs one gunman somewhere to open fire ... The Russians still don't exclude the option of taking Tbilisi."
Russia has said its soldiers have pushed into Georgia from South Ossetia to build a security zone. The peace agreement permits Moscow to patrol a limited buffer zone between South Ossetia and Georgia proper.
But Russian checkpoints now block the main east-west highway, a vital trade route which links Tbilisi with Georgia's Black Sea ports. Russian soldiers have also moved into towns in western Georgia, controlling traffic and movement.